Moderate heat treatment of CoFe Prussian blue analogues for enhanced oxygen evolution reaction performance

Prussian blue analogues (PBAs) with inherent ordered structures and abundant metal ion sites are widely explored as precursors for various electrochemical applications, including oxygen evolution reaction (OER). Using a range of characterization techniques Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron (XPS), diffraction (XRD) energy dispersive (EDS), this work discloses the process replacement K+ by NH4+ in interstitial spaces CoFe PBA hot aqueous urea solution, which influences transformation PBAs under further heat treatment OER performance derivatives. After at 400 °C Ar flow, high-resolution transmission electron microscopy (HRTEM) images reveal that alloy nanoparticles grew on crystalline cubes K+, while become amorphous. Besides, derivative (Ar-U-CoFe PBA) performs better than (Ar-CoFe OER, registering lower overpotential 305 mV 10 mA cm−2, smaller Tafel slope 36.1 dec−1, stability over testing course 20 h 1.0 M KOH. A single-cell alkaline electrolyzer, using Ar-U-CoFe Pt/C anodic cathodic catalyst, respectively, requires an initial cell voltage 1.66 V to achieve 100 cm−2 80 °C, negligible degradation after h.